Anticancer effect of Andrographis paniculata by suppression of tumor altered hypoxia signaling cascade in mouse melanoma cells

Abstract

Background: Intratumor hypoxia, the main factor responsible for the angiogenic switch, represents one of the major events leading to tumor progression. Tumor hypoxia leads to the stabilization of hypoxia-inducible factor-1α (HIF-1α) which influences tumor angiogenesis. The new blood vessels formed by the HIF-1α-vascular endothelial growth factor (VEGF) signaling axis create the tumor microenvironment, which inhibits drug delivery to solid tumors. The present study aimed to investigate the effect of Andrographis paniculata leaf extract as a powerful anticancer agent targeting the HIF-1α-VEGF signaling axis in mouse melanoma cell. Materials and Methods: We induced hypoxia-mimicking conditions in mouse B16 melanoma cell with cobalt chloride. Total RNA was isolated followed by reverse transcriptase polymerase chain reaction to study the transcriptional expressions of HIF-1α and VEGF. Further confirmation of the transcriptional profiling was done at the protein level with Western blot analysis. Expression profiling of transcriptional factors involved in the hypoxia signaling cascade was done. An immunofluorescence study was also used to confirm the results obtained from transcriptional and translational analyses. Results: A. paniculata leaf extract significantly downregulated the expressions of HIF-1α and VEGF both at the transcriptional and translational level. Sp1, p300, CBP expressions were also downregulated, whereas the expression of Sp3 was significantly upregulated by A. paniculata leaf extract in B16 melanoma cells. Conclusion: In the present study, A. paniculata-treated cells demonstrated lower expressions of VEGF and HIF-1α both at the transcriptional and translational level. The mechanism of the downregulation of HIF-1α was probably through the altered expressions of transcriptional factors involved in the hypoxia-signaling cascade.